When bombarding alliance planets through the stG->Planet->boMbardment menu, planetary shields take a lot of punishment and the planet never surrenders before all cities are destroyed, wiping out all alliance troops. That seems like correct behavior according to the manual. However, when bombarding through the Orbit control screen, planetary shields often don't get raised at all or, if already up, absorb one shot and then stop working, and after destroying a few cities the planet will surrender (quicker if I strike the capital), even with a bunch of UGA troops still around, and without having to send down negotiators because it seems to work like an invasion victory. Is this intended behavior?

I had some trouble with 3-E before I realized that this was possible, given that I could not actually more than a few non-Alliance worlds that were TL 4+ to bombard into submission the regular way, and going through the shields takes a lot of time and a full battlegroup resupply, but it seems like cheating to do it this way.

I can record an unlisted video to demonstrate the two approaches and three discrepancies that seem like bugs if my description is unclear. But at least in Centurion and Commander missions:

0. Start a Centurion or Commander mission
1. Orbit and survey a TL4 or TL5 alliance planet
2. stG->Planet->Orbit control
3. Bombard cities from the Orbit control screen with phasers or torps

Expected result 1:
If they have planetary shields, they would raise them

Actual result 1:
They don't raise planetary shields

Expected result 2:
If their planetary shields are up with over 10000 units due to a previous boMbardment, they will protect from several bombardments

Actual result 2:
I get one message about the shield absorbing a few hundred units from the first press of B, and after that B functions as though there were no planetary shields

Expected result 3:
If UGA troops are present, the planet will not surrender due to Bombardment, at least without any Krellan troops present, matching the behavior when stG->Planet->boMbarding.

Actual result 3:
Usually, the planet will surrender before destroying half the cities from there. If the planet has planetary shields, they won't raise them. You also don't have to send down a negotiating party to take control of the planet, though that's a pretty minor task anyway. You receive Krels and Slaves as though it was an invasion victory, but it does CORRECTLY count as a bombardment victory and not count as an invasion victory for mission objectives.